A "bloodpulse wave" is the blood pressure wave, which is pumped out from the heart and propagates through a blood vessel, or the vibration of the blood vessel wall generated by the blood pressure wave. Since various medical information, for example, the vital condition of the heart, can be obtained by detecting and analyzing blood pulse waves, it has been carried out to diagnose blood pulse wave by the diagnostician's sense of touch traditionally in Oriental medicine.
More specifically, the diagnostician presses the patient's wrist by his fingers and measures blood pulse wave of the radial artery by the finger's sense of touch in Oriental medicine. Due to the finger pressure, the amplitude of the sensed pulse wave changes, so that the changing characteristic of the amplitude of pulse wave can be a diagnostic parameter in the field of Oriental medicine.
FIGS. 22A to 22C respectively show curves indicating amplitude variations of the sensed pulse wave due to pressure change. These curves are called "tendency curves" in Oriental medicine.
The tendency curve in FIG. 22A has a peak at the center thereof. That is, when a medium pressure is applied to the artery, pulse wave can be detected clearly. This kind of curve is categorized into a "normal curve", and this is a characteristic of normal pulse wave ("Ping-mai") obtained from a healthy human body.
The tendency curve in FIG. 22B has a peak at the left thereof. This kind of curve is categorized into a "gradual decrease curve". In this case, pulse wave can be detected clearly when a weak pressure is applied, but pulse wave weakens when the applied pressure rises. This phenomenon is called "Hua" and this kind of pulse wave is called "Hua-mai".
The tendency curve in FIG. 22C has a peak at the right thereof. This kind of curve is categorized into an "gradual increase curve". In this case, pulse wave can not be detected clearly when a weak pressure is applied, but it can be detected when the pressure applied by the diagnosticians finger rises. This phenomenon is called "Xuan" and this kind of pulse wave is called "Xuan-mai".
The Hua-mai is caused by an abnormality in the flow of blood in which the movement of the blood through the vessel becomes extremely smooth due to some kinds of illness. The Xuan-mai is on the other hand caused by an increase in the tension in the walls of the blood vessels because of other kinds of illness. Thus, the correlation between the given initial pressure and the wave amplitude is an important factor for evaluating patient's condition in the pulse wave diagnosis.
However, there are individual differences among patients. Namely, there are fat patients and thin patients. In addition, each patient has his or her own muscular and fat distribution and elasticity in the flesh. Therefore, although the same pressure is given, the displacement of the organism tissues is dependent on the individuality. The amplitude of pulse wave relates to the distance between the skin surface and the blood vessel when the pressure is applied, and to the configuration of the pressed blood vessel. In manual diagnosis by a skilled diagnostician, he controls the pressure by himself, thereby judging that the patient's pulse wave belongs to Ping-mai, Hua-mai or, Xuan-mai. Therefore, it is also preferable to optionally adjust the initial pressure given to the measured blood vessel for mechanical diagnosis.
Conventionally, devices for measuring blood pulse wave comprise pressure measuring devices including pressure sensors, such as piezoelectric elements or strain gauges, which can be into contact with the organism's skin, e.g., the skin portion over the radial artery. The pressure sensor is strained due to the stress varying by the pulsation of the blood vessel, and outputs pulsation signals corresponding to the stress fluctuations.
In order to measure pulse wave under stable condition, these pressure measuring devices should be pressed against the organism's skin at a pressure. As disclosed in JP-A-4-102438, JP-A-4-108424, JP-A-4-67839, and JP-A-4-67840, pressure measuring devices are usually mounted on cuffs which are elastic bags wound around the patients, arms, and are pressed on the organisms' surfaces by compulsorily introducing air into the cuffs.
However, it is difficult to adjust the initial pressure on the blood vessel using with such cuffs for pressing the pressure measuring devices on the organisms, surfaces since the flat surfaces of the cuffs transform the tissues in the vicinity of the blood vessels as well as the blood vessels. Even if the same pressure is applied to the cuff, the pressure in the blood vessel is not solely determined. Furthermore, the pressure measuring device mounted on the cuff is difficult to be accurately positioned above the blood vessel, e.g., the radial artery.
Another type of blood pulse wave measuring device comprises a pen-like holder and a pressure sensor mounted on the end of the holder. The pressure sensor is into contact with the patient's skin, e.g., the vicinity of the radial artery, and measures pulse wave according to the pulsation of the blood vessel.
Another type of blood pulse wave measuring device comprises a rubber glove and a strain gauge mounted on the finger sheath of the glove. The diagnostician wears the rubber glove and presses the strain gauge against the skin over the radial artery of the patient using with his finger, whereby the strain gauge detects blood pulse wave.
It is necessary for the diagnostician to hold the sensor above the radial artery of the patient when using such a blood vessel measuring device with the pen-like holder or rubber glove. However, since it is difficult for the diagnostician to continuously hold the sensor, mounted on the finger sheath or the pen end, above the radial artery, the sensor may move from the desirable position above the radial artery and may not measure accurately. If physiological status of organism is analyzed on the basis of inaccurate results obtained by such a measuring device, the analysis may contain some errors.
Accordingly, a pulse wave measuring device with an automatic positioner is proposed in JP-A-1-155828. In the device, while the sensor is moved across the line along the blood vessel, pulse wave is measured at a plurality of positions. The amplitude and other characteristics are analyzed over these positions, so that the best position directly above the blood vessel is detected. Then, the sensor is fixed at the best position to measure blood pulse wave.
However, the technique disclosed in JP-A-1-155828 needs a driver for moving the sensor, and devices for automatically determining the best measuring position. Therefore, the entire device should be enlarged.
It is therefore an object of the present invention to provide blood pulse wave measuring device and a pulsation measuring device, in which a pressure sensor or pulsation sensor can be positioned accurately on the measured subject, and the initial pressure given to the measured subject can be readily and desirably adjusted.
Another object of the present invention is to provide a pressure measuring device in which the energy loss can be reduced.